Generally, wastewater treatment is a process that stabilizes polluted materials in water by a microbial or chemical oxidation-reduction reaction and separates untreated residual materials.
In other words, wastewater treatment is a process that stabilizes and separates properties of the water quality, organic materials, and nutritional materials by various methods. Currently, wastewater treatment is mostly performed by a biological method, and the cost for wastewater treatment is relatively inexpensive.
Such biological wastewater treatment is a method that purifies wastewater by contacting wastewater with carriers having a large amount of microbes.
However, such a conventional biological wastewater treatment may have the following problems.
Firstly, a lot of additional energy is required for raising standard oxygen transfer efficiency (SOTE) because biological wastewater treatment has low standard oxygen transfer efficiency (SOTE).
Secondly, a large-volume reactor is necessary for a conventional biological wastewater treatment because a large amount of microbes should be returned due to losses of microbes in a reactor and inflow amounts of microbes are not as much as returning amounts of microbes when microbes are returned.
Thirdly, decomposing abilities may be deteriorated because microbes of which activities are deteriorated during a precipitation process or which experience a sufficient growth period may flow into an aeration tank.
Fourthly, since fluidity of wastewater in a reactor is low, sludge may be accumulated around carriers after several operations of a plant for wastewater treatment, and an inner part of carriers may become anaerobic for the most part. Consequently, efficiency of a plant for wastewater treatment may be deteriorated.
Fifthly, oxygen dissolution, dissolved oxygen, and speed of mass transfer which is a speed that a substrate transfers to a microbe are low because linear velocity is low during movement of a fluid such as wastewater.
Sixthly, since a reactor is a complete mixture type, reaction induction is inevitable at a low concentration. Accordingly, speed for treating wastewater is low and highly efficient reaction is hard to be obtained at a low concentration.
Seventhly, since a reactor contains the same material, various kinds of microbes are hard to be obtained.